Valorization of lignin waste: high electrochemical capacitance of lignin-derived carbons in aqueous and ionic liquid electrolytes

摘要

This report describes the utilization of waste lignin-derived activated carbons (LACs) as high-energy/high-power electrode materials for electric double layer capacitors (EDLCs). The influence of the carbon-pore structure on the capacitance of the LACs in two aqueous (H _(2) SO _(4) and KCl) and two ionic liquid (1-ethyl-3-methylimidazolium ethylsulfate, [EMIm][EtSO _(4) ], and 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIm][BF _(4) ]) electrolytes is evaluated. In EDLCs containing aqueous H _(2) SO _(4) as the electrolyte, the LACs exhibit specific capacitances of up to 223 F g ~(?1) and good cycling stability, with an energy density of 5.0 W h kg ~(?1) at a power density of 200 W kg ~(?1) . EDLCs containing KCl achieved a specific capacitance of 203 F g ~(?1) , and an energy density of 7.1 W h kg ~(?1) at a power density of 510 W kg ~(?1) . The specific capacitances of the LACs in [EMIm][EtSO _(4) ] and [BMIm][BF _(4) ] were up to 147 F g ~(?1) and 175 F g ~(?1) , respectively. The energy density in the IL electrolytes is up to 25 W h kg ~(?1) at a power density of 500 W kg ~(?1) and 16.4 W h kg ~(?1) at 15 kW kg ~(?1) . We demonstrate that the electrochemical performance of the LACs depends not only the surface area and pore size, but also on the pore-wall thickness.